Originally Posted by fatherjac

I have just installed a new Campagnolo Chorus 12 speed Groupset to my Colnago C60 and I cannot get the rear mech adjusted to eliminate chain skipping/noise on the cassette. I have the 48/32 chainset and 11-34 cassette. I have installed many Campagnolo group sets over many years and never had a problem I couldn't resolve until now. I have used all the normal set up procedures from aligning the first cog, setting the end stops and the B screw etc. I cannot find any adjustment position where the chain runs quietly on all cogs. I can get it to run well on the top 4 and the bottom 4 but the middle 4 of the cassette run noisy. Adjusting the middle cogs leads to misalignment on the top and bottom cogs. I have tried everything I can think of to no avail including

1. checking the hanger alignment and resetting
   
2. checking cable for stickyness
   
3. checking the rear mech hinges for stiffness
   
4. refitting the cassette and trying it on a different wheel
   

I have spent many hours on this and am now well and truly stuck.